Brage NMBUhttp://nmbu.brage.unit.no:80/nmbu-xmlui
Unit Brage is a system for open institutional archives that captures, stores, indexes, preserves, and distributes digital research material produced by the institutions in the Brage Consortium.Sun, 15 Sep 2019 09:44:49 GMT2019-09-15T09:44:49ZCNash - A novel parameter predicting cake solids of dewatered digestateshttp://hdl.handle.net/11250/2616801
CNash - A novel parameter predicting cake solids of dewatered digestates
Svennevik, Oda Marie Kjørlaug; Beck, Greeley; Rus, Ester; Westereng, Bjørge; Higgins, Matthew; Solheim, Odd Egil; Nilsen, Pål Jahre; Horn, Svein Jarle
Efficient digestate dewatering is crucial to reduce the volume and transportation cost of solid residues from anaerobic digestion (AD) plants. Large variations in dewatered cake solids have been reported and predictive models are therefore important in design and operation of such plants. However, current predictive models lack validation across several digestion substrates, pre-treatments and full-scale plants. In this study, we showed that thermogravimetric analysis is a reliable prediction model for dewatered cake solids using digestates from 15 commercial full-scale plants. The tested digestates originated from different substrates, with and without the pre-AD thermal hydrolysis process (THP). Moreover, a novel combined physicochemical parameter (C/N•ash) characterizing different digestate blends was identified by multiplying the C/N ratio with ash content of the dried solids. Using samples from 22 full-scale wastewater, food waste and co-waste plants, a linear relationship was found between C/N•ash and predicted cake solids for digestates with and without pre-AD THP. Pre-AD THP improved predicted cake solids by increasing the amount of free water. However, solids characteristics like C/N ratio and ash content had a more profound influence on the predicted cake solids than pre-AD THP and type of dewatering device. Finally, C/N•ash was shown to have a linear relationship to cake solids and reported polymer dose from eight full-scale pre-AD THP plants. In conclusion, we identified the novel parameter C/N•ash which can be used to predict dewatered cake solids regardless of dewatering device and sludge origin.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/11250/26168012019-01-01T00:00:00ZNutrient effect of various composting methods with and without biochar on soil fertility and maize growthhttp://hdl.handle.net/11250/2616800
Nutrient effect of various composting methods with and without biochar on soil fertility and maize growth
Pandit, Naba Raj; Schmidt, Hans Peter; Mulder, Jan; Hale, Sarah; Husson, Olivier; Cornelissen, Gerard
This work showed for the first time that organic nutrient transformation techniques based on locally available materials (manure, green waste and advanced biochar) can increase fertilizing efficiency of the resulting substrate by a factor of three compared with other organic amendments without biochar. We used three different composting methods to investigate the techniques of organic nutrient transformations; i) conventional composting (composting process completed without turning the piles) ii) aerobic composting (composting process with manual turning of piles) and iii) bokashi composting (anaerobic lacto-fermentation). Composting was carried out in the absence (compost alone) and the presence of biochar (co-composted). Biochar was produced locally from an invasive forest shrub ‘Eupatorium adenophorum’. A pot trial with maize grown in silty loam soil was carried out to investigate the agronomic effect produced using three above-mentioned composting methods that were compared with conventional mineral fertilizers (NPK). Significant effects of co-composted bokashi-biochar (60 t ha−1) were observed on maize growth, which increased biomass by 243% compared to mineral NPK, also showing better growth effects than conventional and aerobic composting amendments. Improved soil available nutrients (available P and other exchangeable base cations (K+, Ca2+ and Mg2+)) were probably the cause of the superior growth effect of co-composted bokashi-biochar.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/11250/26168002019-01-01T00:00:00ZSelection for feed efficiency in Atlantic salmon using individual indicator traits based on stable isotope profilinghttp://hdl.handle.net/11250/2616795
Selection for feed efficiency in Atlantic salmon using individual indicator traits based on stable isotope profiling
Dvergedal, Hanne; Ødegård, Jørgen; Øverland, Margareth; Mydland, Liv Torunn; Klemetsdal, Gunnar
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/11250/26167952019-01-01T00:00:00ZHeritability of head size in a hunted large carnivore, the brown bear (Ursus arctos)http://hdl.handle.net/11250/2616794
Heritability of head size in a hunted large carnivore, the brown bear (Ursus arctos)
Rivrud, Inger Maren; Frank, Shane; Bischof, Richard; Mysterud, Atle; Steyaert, Sam; Hertel, Anne Gabriela; Hagen, Snorre; Eiken, Hans Geir; Swenson, Jon; Zedrosser, Andreas
Wild animal populations experience selection pressures from both natural and anthropogenic sources. The availability of extensive pedigrees is increasing along with our ability to quantify the heritability and evolvability of phenotypic traits and thus the speed and potential for evolutionary change in wild populations. The environment may also affect gene expressions in individuals, which may in turn affect the potential of phenotypic traits to respond to selection. Knowledge about the relationship between the genetic and environmental components of phenotypic variation is particularly relevant, given ongoing anthropogenically driven global change. Using a quantitative genetic mixed model, we disentangled the genetic and environmental components of phenotypic variance in a large carnivore, the brown bear (Ursus arctos). We combined a pedigree covering ~1,500 individual bears over seven generations with location data from 413 bears, as well as data on bear density, habitat characteristics, and climatic conditions. We found a narrow‐sense heritability of 0.24 (95% CrI: 0.06–0.38) for brown bear head size, showing that the trait can respond to selection at a moderate speed. The environment contributed substantially to phenotypic variation, and we partitioned this into birth year (5.9%), nonadditive among‐individual genetic (15.0%), and residual (50.4%) environmental effects. Brown bear head circumference showed an evolvability of 0.2%, which can generate large changes in the trait mean over some hundreds of generations. Our study is among the first to quantify heritability of a trait in a hunted large carnivore population. Such knowledge about the degree to which species experiencing hunting can respond to selection is crucial for conservation and to make informed management decisions. We show that including important environmental variables when analyzing heritability is key to understanding the dynamics of the evolutionary potential of phenotypic traits.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/11250/26167942019-01-01T00:00:00ZControlled infrared heating of an artic meadow: challenge in the vegetation establishment stagehttp://hdl.handle.net/11250/2616793
Controlled infrared heating of an artic meadow: challenge in the vegetation establishment stage
Moni, Christophe; Silvennoinen, Hanna Marika; Kimball, Bruce A.; Fjelldal, Erling; Brenden, Marius; Burud, Ingunn; Flø, Andreas Svarstad; Rasse, Daniel
Background: Global warming is going to affect both agricultural production and carbon storage in soil worldwide. Given the complexity of the soil-plant-atmosphere continuum, in situ experiments of climate warming are necessary to predict responses of plants and emissions of greenhouse gases (GHG) from soils. Arrays of infrared (IR) heaters have been successfully applied in temperate and tropical agro-ecosystems to produce uniform and large increases in canopy surface temperature across research plots. Because this method had not yet been tested in the Arctic where consequences of global warming on GHG emission are expected to be largest, the objective of this work was to test hexagonal arrays of IR heaters to simulate a homogenous 3 °C warming of the surface, i.e. canopy and visible bare soil, of five 10.5-m2 plots in an Arctic meadow of northern Norway. Results: Our results show that the IR warming setup was able to simulate quite accurately the target + 3 °C, thereby enabling us to simulate the extension of the growing season. Meadow yield increased under warming but only through the lengthening of the growing season. Our research also suggests that, when investigating agricultural systems on the Arctic, it is important to start the warming after the vegetation is established,. Indeed, differential emergence of meadow plants impaired the homogeneity of the warming with patches of bare soil being up to 9.5 °C warmer than patches of vegetation. This created a pattern of soil crusting, which further induced spatial heterogeneity of the vegetation. However, in the Arctic these conditions are rather rare as the soil exposed by snow melt is often covered by a layer of senescent vegetation which shelters the soil from direct radiation. Conclusions: Consistent continuous warming can be obtained on average with IR systems in an Arctic meadow, but homogenous spatial distribution requires that the warming must start after canopy closure.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/11250/26167932019-01-01T00:00:00ZEffects of limited volatiles release by plants in tritrophic interactionshttp://hdl.handle.net/11250/2616704
Effects of limited volatiles release by plants in tritrophic interactions
Buonomo, Bruno; Giannino, Francesco; Saussure, Stephanie; Venturino, Ezio
We introduce a mathematical model to describe the tritrophic interaction between crop, pest and the pest natural enemy where the release of Volatile Organic Compounds (VOCs) by crop is taken into account. The VOCs may be considered as an indirect defence mechanism of the plant as they attract the pest natural enemies toward the attacked plants. The model dynamics is studied through qualitative analysis and numerical simulations. The factors that may enhance pest disappearance are identified. In particular, we show that VOCs may have a beneficial effect on the environment since their release may be able to stabilize the model dynamics. Specifically, for the parameter values that we have explored, this effect can arise only when both the phenomena of VOCs basic plant release and VOCs plant release due to pest attack are present.; Effects of limited volatiles release by plants in tritrophic interactions
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/11250/26167042019-01-01T00:00:00ZErythroid Progenitor Cells in Atlantic Salmon (Salmo salar) May Be Persistently and Productively Infected with Piscine Orthoreovirus (PRV)http://hdl.handle.net/11250/2616701
Erythroid Progenitor Cells in Atlantic Salmon (Salmo salar) May Be Persistently and Productively Infected with Piscine Orthoreovirus (PRV)
Malik, Muhammad Salman; Bjørgen, Håvard; Kannimuthu, Dhamotharan; Wessel, Øystein; Koppang, Erling Olaf; Di Cicco, Emiliano; Hansen, Elisabeth Furuseth; Dahle, Maria K; Rimstad, Espen
Piscine orthoreovirus (PRV-1) can cause heart and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon (Salmo salar). The virus targets erythrocytes in the acute peak phase, followed by cardiomyocytes, before the infection subsides into persistence. The persistent phase is characterized by high level of viral RNA, but low level of viral protein. The origin and nature of persistent PRV-1 are not clear. Here, we analyzed for viral persistence and activity in various tissues and cell types in experimentally infected Atlantic salmon. Plasma contained PRV-1 genomic dsRNA throughout an 18-week long infection trial, indicating that viral particles are continuously produced and released. The highest level of PRV-1 RNA in the persistent phase was found in kidney. The level of PRV-1 ssRNA transcripts in kidney was significantly higher than that of blood cells in the persistent phase. In-situ hybridization assays confirmed that PRV-1 RNA was present in erythroid progenitor cells, erythrocytes, macrophages, melano-macrophages and in some additional un-characterized cells in kidney. These results show that PRV-1 establishes a productive, persistent infection in Atlantic salmon and that erythrocyte progenitor cells are PRV target cells.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/11250/26167012019-01-01T00:00:00ZA computational model for gonadotropin releasing cells in the teleost fish medakahttp://hdl.handle.net/11250/2616699
A computational model for gonadotropin releasing cells in the teleost fish medaka
Halnes, Geir; Tennøe, Simen; Haug, Trude; Einevoll, Gaute; Weltzien, Finn-Arne; Hodne, Kjetil
Pituitary endocrine cells fire action potentials (APs) to regulate their cytosolic Ca2+ concentration and hormone secretion rate. Depending on animal species, cell type, and biological conditions, pituitary APs are generated either by TTX-sensitive Na+ currents (INa), high-voltage activated Ca2+ currents (ICa), or by a combination of the two. Previous computational models of pituitary cells have mainly been based on data from rats, where INa is largely inactivated at the resting potential, and spontaneous APs are predominantly mediated by ICa. Unlike in rats, spontaneous INa-mediated APs are consistently seen in pituitary cells of several other animal species, including several species of fish. In the current work we develop a computational model of gonadotropin releasing cells in the teleost fish medaka (Oryzias latipes). The model stands out from previous modeling efforts by being (1) the first model of a pituitary cell in teleosts, (2) the first pituitary cell model that fires sponateous APs that are predominantly mediated by INa, and (3) the first pituitary cell model where the kinetics of the depolarizing currents, INa and ICa, are directly fitted to voltage-clamp data. We explore the firing properties of the model, and compare it to the properties of previous models that fire ICa-based APs. We put a particular focus on how the big conductance K+ current (IBK) modulates the AP shape. Interestingly, we find that IBK can prolong AP duration in models that fire ICa-based APs, while it consistently shortens the duration of the predominantly INa-mediated APs in the medaka gonadotroph model. Although the model is constrained to experimental data from gonadotroph cells in medaka, it may likely provide insights also into other pituitary cell types that fire INa-mediated APs.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/11250/26166992019-01-01T00:00:00ZProtein fractionation by microfiltration in high-protein yogurt processinghttp://hdl.handle.net/11250/2616492
Protein fractionation by microfiltration in high-protein yogurt processing
Jørgensen, Camilla Elise
The main objective of the work presented in this thesis was to investigate the optimization of the microfiltration (MF) process in the production of high-protein yogurts (≥ 5.6% protein). High-protein yogurts have gained popularity during the last decade. However, research-based information about the impact of processing conditions on rheology, structure, and sensory properties of high-protein yogurt is limited.
The main proteins in milk, the caseins and whey proteins, can be fractionated into a casein-rich retentate and a permeate containing native whey proteins with the use of MF with membranes of 0.05–0.20 µm pore size. The native whey proteins can be further concentrated with ultrafiltration to a native whey protein concentrate (NWPC).
The effect of ceramic membrane pore size and filtration temperature on protein fractionation of skim milk by MF in a uniform transmembrane pressure system was investigated. An industrial MF application was modeled by performing MF with a constant permeate flux to a volume concentration factor of 2.5. Removal of native whey proteins increased with increasing pore size, giving the permeate from MF with the 0.20-µm membrane a significantly higher concentration of native whey proteins than the permeates from the 0.05- and 0.10-µm membranes (0.50, 0.24, and 0.39%, respectively). Significant amounts of small casein micelles (~130 nm) permeated the 0.20-µm membrane, resulting in a permeate with a white appearance, a casein content of 1.4%, and a casein distribution (αs2-casein (CN): αs1-CN: κ-CN: β-CN) similar to that of skim milk. The 0.10-µm membrane was found to be the most optimal for protein fractionation of skim milk into a casein concentrate and a permeate with native whey proteins and free from casein. Increasing the temperature of MF from 50 to 60°C when using the 0.10-µm membrane caused a reduction in native whey protein permeation and a steeper increase in transmembrane pressure during filtration. This was explained by potential interactions between whey proteins with casein micelles deposited on the membrane surface.
The permeate with native whey proteins from MF of skim milk was concentrated to a NWPC by ultrafiltration. Yogurt milk bases with ~8% protein were made by adding NWPC to casein concentrate in different whey protein:casein ratios (10:90–45:55). The degree of whey protein denaturation was then controlled by subjecting the yogurt milk base to varying degrees of high temperatures. The denaturation status of the whey proteins and the ratio of whey protein to casein significantly influenced the microstructure, coagulum particle size, storage modulus (G’), firmness, and sensory properties of the resulting stirred, high-protein yogurts. The addition of NWPC in low or moderate levels (whey protein to casein ratio 25:75 or 35:65, respectively) in combination with heat treatment of the yogurt milk base at 75°C for 5 min yielded yogurts with significantly lower firmness, lower G’, less coarse and granular appearances, and smoother consistencies, compared with corresponding yogurts produced from yogurt milk bases heat-treated at 95°C for 5 min or with control yogurts (no addition of NWPC). The addition of NWPC to the yogurt milk base after heat treatment or to the fermented yogurt before cooling gave stirred yogurts with unacceptable sensory appearances and consistencies. Thus, sensory acceptable high-protein yogurts, characterized as smooth and viscous, with considerable amounts of undenatured whey proteins (13-15 mg mL-1) (approximately 50% of the available whey proteins in the yogurt) could be produced by adding NWPC to the yogurt milk base and by controlling the denaturation degree of the whey proteins by heat treatment.
MF with 0.20-µm membranes was used to fractionate skim milk with an average casein micelle size of ~174 nm into a retentate and a permeate containing “large” (~183 nm) and “small” (~129 nm) casein micelles, respectively. The permeate with small casein micelles was further concentrated with 0.10-µm membranes. Casein micelle size of yogurt milk bases significantly influenced the rheological properties of set type, high-protein yogurts (~5.6% protein). Yogurt milk base with small casein micelles yielded yogurts with higher storage modulus (G’) and higher firmness than yogurt milk base with large casein micelles. Increased gelation capacity of small casein micelles can be explained by the increased amount of κ-CN.
The results obtained in this study revealed that MF of skim milk before fermentation can be utilized when producing high-protein yogurts. The choice of membrane pore size influences the protein composition of the resulting fractions, and thus the functional properties. High-protein yogurts with various properties regarding composition, structure, rheology, and sensory properties can be tailored with the use of retentates and permeates from protein fractionation by MF, and by controlling the degree of whey protein denaturation by heat treatment of the yogurt milk base.; Hovedmålet til dette forskningsprosjektet var å undersøke hvordan mikrofiltrering (MF) kan optimaliseres og benyttes ved produksjon av proteinrik yoghurt (≥ 5,6 % protein). Gjennom det siste tiåret har yoghurt med høyt proteininnhold blitt stadig mer populært. Det er imidlertid begrenset forskningsbasert informasjon om innvirkningen av ulike prosessbetingelser på reologiske, strukturelle og sensoriske egenskaper til proteinrik yoghurt.
Melkas hovedproteiner, kaseiner og myseproteiner, kan ved bruk av MF og membraner med porestørrelse fra 0,05 til 0,20 µm fraksjoneres til et kaseinrikt retentat og et permeat som inneholder native myseproteiner. De native myseproteinene kan videre konsentreres til et nativt myseproteinkonsentrat ved bruk av ultrafiltrering.
Effekten av porestørrelsen til keramiske membraner og filtreringstemperatur ble undersøkt ved proteinfraksjonering av melk ved bruk av et MF-system med et uniformt transmembrantrykk. MF av melk ble utført ved en konstant permeatfluks til en volumkonsentrasjonsfaktor tilsvarende 2,5 for å etterligne industriell anvendelse av MF. Mengden native myseproteiner som ble fjernet fra melka økte med økende membranporestørrelse. Det var en signifikant høyere konsentrasjon av native myseproteiner i permeatet fra MF med 0,20 µm-membraner enn i permeatene fra MF med 0,05 µm- og 0,10 µm-membraner (henholdsvis 0,50, 0,24 og 0,39 %). Betydelige mengder små kaseinmiceller (~130 nm) passerte gjennom 0,20 µm-membranen og ga et permeat med 1,4 % kasein. Dette resulterte i et permeat med et hvitt utseende og en kaseinsammensetning (αs2-kasein (KN): αs1-KN: κ-KN: β-KN) lik den som er i melk. Forsøket viste at membranen med 0,10 µm porestørrelse var den best egnede til å fraksjonere melk til et kaseinkonsentrat og et kaseinfritt permeat inneholdende native myseproteiner. En økning av filtreringstemperaturen fra 50 til 60 °C ved bruk av 0,10 µm-membranen førte til en reduksjon i mengde native myseproteiner som passerte gjennom membranen, samt en kraftigere økning i transmembrantrykk under filtreringen. Dette funnet ble tilskrevet potensielle interaksjoner mellom myseproteiner og kaseinmiceller som avsettes på membranens overflate.
De native myseproteinene i permeatet fra MF av skummet melk ble konsentrert til et nativt myseproteinkonsentrat ved bruk av ultrafiltrering. Yoghurtmelk med ~8 % protein ble laget ved å tilsette nativt myseproteinkonsentrat til kaseinkonsentrat i ulike myseprotein:kasein-forhold (10:90–45:55). Denatureringsgraden til myseproteinene ble kontrollert ved å utsette yoghurtmelka for varierende grad av høye temperaturer. Denatureringsgrad og myseprotein:kasein-forhold hadde signifikant effekt på mikrostruktur, gelpartikkelstørrelse, elastiske egenskaper (G’), grad av fasthet og sensoriske egenskaper til proteinrik yoghurt. Tilsetning av nativt myseproteinkonsentrat i lave eller moderate mengder (henholdsvis myseprotein:kasein-forhold 25:75 eller 35:65) i kombinasjon med varmebehandling av yoghurtmelka ved 75 °C i 5 min, resulterte i yoghurt med signifikant lavere grad av fasthet og elastiske egenskaper (G’), mindre klumpete og fnokkete utseende og glattere konsistens, sammenliknet med tilsvarende yoghurt framstilt av yoghurtmelk varmebehandlet ved 95 °C i 5 min eller kontroll-yoghurten som ikke var tilsatt nativt myseproteinkonsentrat. Tilsetning av nativt myseproteinkonsentrat til yoghurtmelka etter varmebehandling, eller til den fermenterte yoghurten før avkjøling, ga en rørt yoghurt med sensorisk uakseptabelt utseende og konsistens. Viskøs og glatt proteinrik yoghurt med et betydelig innhold av native myseproteiner (13-15 mg mL-1, omtrent 50% av de tilstedeværende myseproteinene) kunne framstilles ved å tilsette nativt myseproteinkonsentrat til yoghurtmelka og ved å kontrollere myseproteinenes denatureringsgrad under varmebehandlingen av yoghurtmelka.
MF med 0,20 µm-membraner ble benyttet til å fraksjonere skummet melk med en gjennomsnittlig kaseinmicellestørrelse tilnærmet 174 nm til et retentat og et permeat med henholdsvis «store» (~183 nm) og «små» (~129 nm) kaseinmiceller. Permeatet med de små kaseinmicellene ble videre konsentrert opp ved bruk av 0,10 µm-membraner. Yoghurtmelkas kaseinmicellestørrelse hadde signifikant innvirkning på de reologiske egenskapene til en set-type (urørt) proteinrik yoghurt (~5,6 % protein). Yoghurtmelka med små kaseinmiceller ga yoghurt som var fastere og hadde høyere grad av elastiske egenskaper (G’) enn yoghurtmelka med store kaseinmiceller. De små kaseinmicellenes forbedrede evne til å danne gel ble koblet til det økte innholdet av κ-KN.
Resultatene fra dette arbeidet har vist at MF av skummet melk før fermentering kan benyttes til framstilling av proteinrik yoghurt. Membranenes porestørrelse påvirker proteinsammensetningen til fraksjonene, og derved deres funksjonelle egenskaper. Anvendelse av fraksjoner fra MF av melk, og kontroll av myseproteiners denatureringsgrad under varmebehandling av yoghurtmelk, kan gi et bredt spekter av proteinrike yoghurtvarianter med ulik proteinsammensetning og sensoriske egenskaper (både struktur og konsistens).
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/11250/26164922017-01-01T00:00:00ZAn experimental study on rotor-wake interactions of wind turbineshttp://hdl.handle.net/11250/2614550
An experimental study on rotor-wake interactions of wind turbines
Mühle, Franz Volker
Interactions of wind turbine wakes with downstream turbines can reduce a wind farm’s
power production and increase loads on the individual turbines. For the purpose of
wind farm optimization, different aerodynamic approaches to modify the performance
and wake flow of one or two model wind turbines have been tested in a number of wind
tunnel experiments.
In a first set of measurements, different modifications of the rotor design to limit wake
effects are studied. Herein, the effect of the blade number on the wake development
is studied by comparing the wake properties behind 2- and 3-bladed model wind
turbines. Also, the influence of the rotational direction is investigated by comparing
the performance of an aligned two-turbine array with co- and counter-rotating rotors.
Moreover, the effect of winglets on the performance and vortex interaction in the wake
is assessed. For this purpose, a new rotor with aerodynamically optimized winglets has
been designed. The performance of the rotor is compared to a reference rotor without
winglets and effects on the vortex interaction and velocity recovery in the wake are
investigated.
The second set of measurements investigated the control of the model wind turbines
by intentional yaw misalignment. Therefore, the wake flow behind a yawed turbine
exposed to different inflow conditions is measured, while also the power and loads on
a two-turbine array are analyzed for varying separation distances, lateral offsets and
yaw angles. Selected test cases are furthermore provided for validation purposes of
CFD codes. In a Blind test experiment, performance and wake data are compared to
computational results from external groups.
All the experiments have been carried out in the closed-loop wind tunnel at NTNU
in Trondheim. The wakes were investigated for uniformly distributed and sheared
inflow velocity profiles with different turbulence intensities ranging from 0.23% to
10.0%. During the project different rotor designs from 2- to 3-bladed rotors, all with
a diameter of D = 0.9 m, are investigated. The velocities in the wake are measured
using a 2-component laser Doppler velocimetry system or a Cobra probe, which is used
to extract phase-averaged information from the wake flow.
The potential of the blade number and opposite rotational directions in turbine
array are found not to have a significant potential for the optimization of a wind farm.
While not affecting the mean velocity distribution, the blade number is observed to
influence to turbulence peak levels in the wake. An opposite rotation of the downstream
turbine is assessed only to be effective for very small turbine separation distances,
where the energy contained in the wake swirl of the upstream turbine can be extracted.
The design of aerodynamically optimized winglets could rise the power coefficient CP
of a single rotor by 8.9%, whereas the thrust coefficient CT only increased by 7.4%.
Winglets are furthermore found to accelerate the tip vortex interaction in the wake,
leading to a local shear layer enlargement and earlier wake recovery. In a wind farm,
rotors with winglets extract more energy and leave a similar amount of kinetic energy
in the wake for potential downstream turbines. Yaw control is found to have the
largest potential for the optimization of wind farms. The total power of an aligned
two-turbine array is assessed to increase up to 11% by deflecting the upstream turbine’s
wake laterally though an intentional yaw misalignment. However, yaw moments on
yawed turbines and turbines operating in a partial wake are observed to increase,
showing the importance of considering loads for yaw control. Finally, the comparison
of experimental data to numerical predictions in the Blind test confirmed the strength
of codes based on Large-Eddy Simulations (LES) in predicting mean velocity and
turbulent kinetic energy levels in the wake precisely.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/11250/26145502018-01-01T00:00:00Z